Gaseous reservoir and method



United States Patent M 3,098,166 GASEOUS RESERVOIR AND METHOD Seymour Goldberg, Lexington, Mass., assiguor to Edgerton, Germeshausen & Grier, Inc., Boston, Mass, a corporation of Massachusetts Filed July 11, 1960, Ser. No. 42,018 9 Claims. (Cl. 3131'79) The present invention relates to gaseous-discharge devices and the like and, more particularly, to reservoirs for supplying gas in such devices.

When gaseous-discharge devices, such as, for example, rectifiers and thyratrons, are operated, appreciable pressure fluctuations occur during the initial instants of operation. Pressure variations also occur during subsequent life-time operation of such devices. The processes involved in such variations, including variations caused by so-called cleanup phenomena, are imperfectly understood at present so that resort has been had to the use of pressure-equalizing reservoirs of gas within the gaseousdischarge device. Ideally, by supplying additional gas to the device to replace cleanup losses, the reservoir should maintain a constant equilibrium pressure in the tube. Heretofore, in commercial practice, an approximation only to such an ideal has been obtained by employing, for example, a heated titanium reservoir, or a heated zirconium reservoir but not in accordance with the invention disclosed herein, containing occluded or absorbed hydrogen gas.

Unfortunately, however, the characteristics of titanium and zirconium are such that, at the operating ambient temperatures and pressures required in commerciallyavailable gaseous-discharge devices, the equilibrium dissociation pressure of the reservoir decreases rather steeply as the absorbed or occluded gas is released and lost to the cleanup process, so that a close approximation to the ideal for supplying additional gas from the reservoir without varying the pressure in the tube has not been achieved. In addition, relatively small atomic ratios of gas are 0"- cluded in such reservoirs.

A better approximation to the ideal has been obtained by operating a rare-earth reservoir member within a temperature range in which the equilibrium-dissociation-pressure lies within the required predetermined pressure limits as disclosed in United States Letters Patent No. 2,919,368, issued on December 29, 1959, to Seymour Goldberg et a1. However, it has been found that said rare-earths are difiicult to work commercially, are expensive, and are therefore, in some cases, undesirable for use in commercial quantities.

An object of the present invention, is to provide a new and improved method of gas supply of the abovedescribed character that shall not be subject to these disadvantages; but that shall, to the contrary, provide for release of occluded or absorbed gas without substantial change in pressure for the required temperatures and pressures, shall do so while permitting of greatly increased atomic ratios of absorbed gas in the reservoir, and shall utilize a material that is easily worked in commercially available quantities and is much less expensive. In summary, this end is achieved by operating a zirconium reservoir member within a temperature range in which the equilibrium-dissociation-pressure as read from the plateau region of a graph of equilibrium-dissociationpressure versus atomic ratio of absorbed gas, lies within the required predetermined pressure limits. The term atomic ratio as used herein is intended to mean the number of absorbed gas atoms per atom of metal.

A further object is to provide a new and improved gaseous-discharge device employing such a novei reservoir.

3,098,166 Patented July 16, 1963 Still another object is to provide a novel gas-supply apparatus of more general utility, as well.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawings, FIG. 1 of which is a graph illustrating the before-mentioned equilibrium-dissociationpressure versus atomic ratio of absorbed gas characteristics; and

FIG. 2 is a longitudinal section of a preferred reservoir construction embodied in a gaseous-discharge device.

Referring to FIG. 1, it will be observed that in the preferred 0.1 to 1.0 millimeter pressure-limit range P of, for example, hydrogen rectifiers and thyratrons, such as those described in United States Letters Patent No. 2,937,302, issued on May 17, 1960, to the said Seymour Goldberg, a prior-art titanium reservoir containing absorbed hydrogen gas operates on the initial steeply rising portion I of its equilibrium-dissociation pressure (plotted in millimeters along the ordinate) versus atomic ratio of absorbed gas (plotted along the abscissa) characteristic. This characteristic applies for an operating temperature of the reservoir sufliciently high to minimize the eiiects of ambient temperature variations in such prior art gaseous-discharge devices; namely, a reservoir temperature in the neighborhood of 1000 K. The initial portion I is then followed by a horizontal plateau region I, Where, as the atomic ratio of absorbed gas varies, substantially no change in equilibrium dissociation pressure occurs. The characteristic then rapidly rises to the far right. Clearly the plateau region I is the desirable operating portion of the characteristic for the purposes of the pres ent invention. Unfortunately, at the 1000 K. temperature, that plateau I can only be obtained for a high 5.0 millimeters of pressure, entirely outside the required pressure limits P. Even if the higher pressure were useful, moreover, the plateau only exists for a very limited region of from about .05 to about .25 atomic ratio of absorbed gas, providing very limited reservoir capacity. In the region I, moreover, only a maximum of .025 atomic ratio gas-absorption capacity exists, and, as before stated, as gas is released, the pressure drops sharply.

It has been discovered, however, that zirconium can be operated in a high gaseous-discharge device temperature range to produce plateau regions in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic that lie well Within the required pressure limits P. Moreover, such plateau regions were never before utilized, as far as can be ascertained, because, probably, zirconium reservoirs were heretofore always operated outside said temperature range. More than this, said plateau regions are almost as extensive as those of the rare-earth reservoirs disclosed in the former-mentioned United States Letters Patent.

Specifically, in the case of hydrogen rectifiers, thyratrons and similar gaseous-discharge devices, it has been discovered that zirconium has the property of providing plateau regions within the preferred pressure range P Within an operating temperature range of from approximately 825 K. to 950 K. At l000 K. and 1075 K. the plateaus (not shown) occur at well over 10 millimeters of pressure. As shown in FIG. 1, a horizontal plateau region for zirconium occurs at a pressure of about one millimeter at approximately 925 K. and for a range of from 0.1 to approximately 0.7 atomic ratio of absorbed hydrogen gas. Similar plateau regions for zirconium are illustrated at operating tube pressures of one-half millimeter and one-tenth of a millimeter for operating tube temperatures of approximately 875 K. and 850 K. respectively.

The reservoir of the present invention is shown in FIG.

2 embodied in a ceramic-vessel thyratron-type tube having a cup-shaped anode electrode 1, an inverted cupshaped control electrode 3 and a vane-type cathode electrode 5, as described in the latter-mentioned United States Letters Patent. These three electrodes are provided with flanges 1, 3, sealed between ceramic-vessel Wall sections 2 as more fully set forth in the latter-mentioned United States Letters Patent. The control electrode 3 may be apertured as at 7 and disposed close to the anode 1, and a grid baflie 9, overlying the apertures 7 may also be provided. A cathode baflle 11 may also be employed. A fuller description of the tube and further details of its construction are omitted in order not to detract from the novel features of the present invention.

The reservoir 4 comprises a cup 6 containing the hydrogen-gas-saturated zirconium 6'. The upper cover 8 is apertured and covered by a Wire mesh screen 10, having a lid 18 attached by a porous weld thereto, thus providing a gas diffusion outlet for the reservoir. A spiral heater l2, energizable by conductors 14 and 16 (the latter of which communicates with the cathode-cup flange 5 and the former of which may extend outside the base of the tube), will heat the reservoir to the required temperature. The height of the reservoir chamber 6 is intentionally made small so that the length of the diffusion path from any point of the chamber is short. The short diffusion path and the proximity of the heater winding 12 provide improved thermal efliciency and warmup. A heat-retaining bafiie 20 may also be employed.

While the invention has been described in connection with a particular type of gaseous-discharge device, it is to be understood that it is also useful with other types of tubes and devices, and, from a more broad point of view, is useful in general as a source of gas that can supply gas without changing the equilibrium dissociation pressure.

Further modifications will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A gas reservoir for a closed vessel that is to remain pressurized within predetermined pressure limits, having, in combination, a member comprising zirconium containing absorbed gas, and means for operating the member within a range of temperature in which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic thereof lies within the said predetermined pressure limits and within the atomic ratio range of approximately 0.2 to 1.4.

2. A gas reservoir for a closed vessel that is to remain pressurized within predetermined pressure limits, having, in combination, a member comprising zirconium cont-aining absorbed hydrogen gas, and means for operating the member within a range of temperature in which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed hydrogen gas characteristic thereof lies within the said predetermined pressure limits and within the atomic ratio range of approximately 0.2 to 1.4.

3. A gas reservoir for a closed vessel that is to remain pressurized within predetermined pressure limits of from substantially one-tenth to substantially one millimeter of pressure, having, in combination, a member comprising zirconium containing absorbed hydrogen gas, and means for operating the member at a temperature between 850 and 925 degrees Kelvin whereby the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed hydrogen gas characteristic thereof lies within the said predetermined pressure limits and Within the atomic ratio range of approximately 0.2 to 1.4.

4. A gaseous-discharge device comprising a closed vessel containing a plurality of electrodes and a hydrogen gaseous medium of predetermined pressure, a gas reservoir member within the vessel comprising zirconium containing absorbed hydrogen gas, and means for operating the member at a temperature at which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic thereof occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.4.

5. A gaseous-discharge device comprising a closed vessel containing a plurality of electrodes and a gaseous medium of predetermined pressure, a gas reservoir within the vessel comprising zirconium containing absorbed gas and disposed within a container having a diffusion outlet, and means for heating the reservoir to a temperature at which the plateau in the equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic thereof occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.4.

6. A device as claimed in claim 4 and in which the predetermined pressure is within the range of from substantially one-tenth to substantially one millimeter of pressure.

7. A device as claimed in claim 6- and in which the said temperature is between 850 and 925 degrees Kelvin.

8. A hydrogen discharge device comprising a closed vessel containing at least an anode and a cathode and filled with hydrogen gas of predetermined pressure, a gas reservoir disposed within the vessel on the opposite side of the cathode from the anode and comprising zirconium containing absorbed hydrogen gas, and means for heating the reservoir at a temperature at which the plateau in the zirconium equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.4.

9. A hydrogen discharge device comprising a closed vessel containing at least an anode and a cathode and filled with hydrogen gas of predetermined pressure, a gas reservoir disposed within the vessel and comprising zirconium containing absorbed hydrogen gas, and means for heating the reservoir at a temperature at which the plateau in the zirconium equilibrium-dissociation-pressure versus atomic ratio of absorbed gas characteristic occurs at substantially the said predetermined pressure and within the atomic ratio range of approximately 0.2 to 1.4.

References Cited in the file of this patent UNITED STATES PATENTS 2,804,563 Palmer Aug. 27, 1957 2,890,319 Watrous June 9, 1959 2,919,368 Goldberg et a1. Dec. 29, 1959 

1. A GAS RESERVOIR FOR A CLOSED VESSEL THAT IS TO REMAIN PRESSURIZED WITHIN PREDETERMINED PRESSURE LIMITS, HAVING, IN COMBINATION, A MEMBER COMPRISING ZIRCONIUM CONTAINING ABSORBED GAS, AND MEANS FOR OPERATING THE MEMBER WITHIN A RANGE OF TEMPERATURE IN WHICH THE PLATEAU IN THE EQUILIBRIUM-DISSOCIATION-PRESSURE VERSUS ATOMIC RATIO OF ABSORBED GAS CHARACTERISTIC THEREOF LIES WITHIN THE SAID PREDETERMINED PRESSURE LIMITS AND WITHIN THE ATOMIC RATIO RANGE OF APPROXIMATELY 0.2 TO 1.4. 